This invention relates to a tool insert.
Abrasive compacts are used extensively in cutting, milling, grinding, drilling and other abrasive operations. The abrasive compacts consist of a mass of diamond or cubic boron nitride particles bonded into a coherent, polycrystalline hard conglomerate. The abrasive particle content of abrasive compacts is high and there is an extensive amount of direct particle-to-particle bonding. Abrasive compacts are made under elevated temperature and pressure conditions at which the abrasive particle, be it diamond or cubic boron nitride, is crystallographically stable. Abrasive compacts tend to be brittle and in use they are frequently supported by being bonded to a cemented carbide substrate. Such supported abrasive compacts are known in the art as composite abrasive compacts. The composite abrasive compact may be used as such in the working surface of an abrasive tool.
Composite diamond abrasive compacts are generally manufactured by placing a layer of diamond particles on a cemented carbide body to form an unbonded assembly and then subjecting that unbonded assembly to elevated temperature and pressure conditions at which diamond is crystallographically stable. Cobalt from the carbide substrate infiltrates the diamond mass during the compact manufacture. In so doing, the carbide substrate in the region of the compact/substrate interface is depleted of cobalt giving rise to stresses in the substrate. These stresses can lead to failure of the composite compact during use.
U.S. Pat. No. 4,592,433 describes a cutting blank comprising a substrate formed of cemented carbide and including a cutting surface. A plurality of shallow grooves are formed in the cutting surface and strips of diamond compact are disposed in the grooves. The strips may be arranged in various patterns. In use, the carbide material wears away exposing the diamond strips which cut through a substrate in a rake or claw-like manner. The relatively soft carbide material dominates in the cutting surface so that the harder diamond strips can be exposed, in use.
U.S. Pat. No. 5,154,245 discloses rock bit buttons of cemented carbide containing a plurality of polycrystalline diamond bodies, each of which is completely surrounded by cemented carbide. Thus, there are a plurality of polycrystalline diamond islands in a cemented carbide working surface.
U.S. Pat. No. 4,997,049 discloses a cemented carbide tool insert having a recess with sloping sides formed therein and in which an abrasive compact is located. In one embodiment the recess is an annulus located in one of the carbide end surfaces.